Oxidation resistant alloys

ABSTRACT

A weldable oxidation resistant cobalt-base alloy is provided containing a small but effective addition of lanthanum preferably in the range of 0.001 to 0.018 percent by weight.

United States Patent 191 Klein et al.

[451 Apr. 9, 1974 OXIDATION RESISTANT ALLOYS [75] Inventors: Howard Joseph Klein; Robert B. H.

l-Ierchenroeder, both of Kokomo,

Ind.

[73] Assignee: Cabot Corporation, Kokomo, Ind.

[22] Filed: Oct. 24, 1972 21 1 App]. No.: 299,665

[52] U.S. Cl. 75/171 [51] Int. Cl. C22c 19/00 [58] Field of Search 75/l7l, 170; 148/32, 32.5

[56] References Cited UNITED STATES PATENTS 3,4I8,I I I I2/I968 Herchenroeder 75/171 Primary Examiner-Richard 0. Dean A weldable oxidation resistant cobalt-base alloy is provided containing a small but effective addition of Ianthanum preferably in the range of 0.001 to 0.018 percent by weight.

5 Claims, 4 Drawing Figures 2000 DYNAMIC OXIDATION TEST FINAL ALUMINUM CONTENT I2- :7 E S E IO- V In in 3 8 I 9 Lu 3 I I l I j 0.20 0.25 0.30 0,35 0.45

ALUMINUM CONTENT PERCENT PATENTEDAPR 9 I974 SHEEI 1 [1F 4 2 |/2-|-. DIE BLOCK LANTHANUM,PERCENT FigJ.

AVERAGE TOTAL CRACK LENGTH (MILS) PATENTEU APR 9 I974 3802,8795 SHEET 2 BF 4 4 IN. DIE BLOCK LANTHANUM, PERCENT Fig.2.

MILS LOSS PER SIDE SH'tET 3 BF 4 2|OOF.STATIC OXIDATION TEST A 0 0.005 La mooo- El/v00 La l i l JO .20 .30 .40 .50

ALUMINUM CONTENT PERCENT Fig.3.

2000" DYNAMIC ox|0Ano- TEST FINAL ALUMINUM CONTENT El -0.0I La WEIGHT LOSS (mg/cm?) l l I l O 0 .05 0J0. 0.:5 0.20 0.25 0.30 0.35 0.45

ALUMINUM CONTENT PERCENT Fig.4.

1 OXIDATION RESISTANT ALLOYS This invention relates to oxidation resistant alloys and particularly to improved oxidation resistant cobalt alloys specifically cobalt-base alloys containing a small, but effective, addition of lanthanum.

US. Pat. No. 3,418,11 l discloses a cobalt-base alloy containing lanthanum as a modifying element to In order to illustrate the unusual results obtained by our invention a series of heats were melted with varying amounts of lanthanum and aluminum. The heats were all prepared by air or vacuum induction melting followed by electroslag remelting to produce the final alloy. The various test samples thus obtained had the compositions set out in Table l hereafter.

TABLE I CHEMICAL COMPOSlTlON F ALLOYS IN WEIGHT Alloy C Mn Si s Cr Ni w L3 A1 B Fe Co* A .08 .66 .34 .010 21.60 22.30 14.05 .005 0.23 .001 2.21 B31 8 .08 .66 .33 .009 21.50 22.30 14.05 .005 0.04 2.21 Bal C .08 .62 .36 .003 21.20 22.80 13.85 .012 .16 1.96 831 D .10 .64 .36 .003 21.20 22.70 13.85 .008 .43 003 1.96 Bal E .09 .54 .47 .006 22.40 22.30 14.25 .010 .08 1.50 831 F .09 .64 .46 .006 22.50 22.30 14.20 .010 .19 .003 1.50 B31 0 .09 .70 .47 .006 22.50 22.10 14.15 .011 .31 1.46 B31 H .09 .68 .48 .007 22.50 22.20 14.15 .010 .43 1.48 Hal 1 .12 .80 .26 ND 22.30 21.20 13.80 .005 .02 ND 2.10 Bal 1 1 .08 .66 .32 .006 21.90 22.40 14.05 .010 .01 ND 2.33 B31 .12 .90 .28 ND 22.10 21.20 13.80 .005 .02 ND 3.22 Bal J-l .08 .70 .35 .006 21 .90 22.30 14.05 .005 .02 ND 2.36 B31 K .08 .66 .34 ND 21.60 22.30 14.05 .005 .01 .001 2.21 Bal L .08 .66 .31 .010 22.00 22.30 14.15 .005 .01 .001 2.24 B31 M .09 .65 .24 .001 21.50 21.80 14.00 .02 0.08 .001 1.90 B31 N .10 .59 .22 .001 21.94 22.15 14.11 .03 .05 .001 1.38 Bal o .09 .62 .29 .006 20.60 22.70 13.45 .04 0.28 .004 2.06 1331 P .10 .66 .44 .001 21.82 21.87 13.85 .05 0.19 .001 1.40 Bal Q .07 .58 .35 .005 21.90 21.90 14.35 .06 0.11 91 2.06 Bal ND Not determined Balance cobalt and incidental impurit ig W prove the oxidation resistance of this class of superal- Of these alloys the first twelve were tested for oxidaloy. A commercial alloy according to U.S. Pat. No. 3,418,111 is known in the art as alloy 188 and is described in AMS 5608.

We have found that extraordinarily improved results are obtained by maintaining the lanthanum levels in the range about 0.001 to 0.018 percent while maintaining the aluminum content in the range of about 0.02 per-. cent to about 0.5 percent. All composition values herein stated are given in percent by weight. We have found that by maintaining the lanthanum in this very narrow range while maintaining at least 0.02 percent aluminum in the alloy we can obtain far more consistent and uniform improvement as well as a markedly superior product over that heretofore available.

We have also found that, while the alloys of this invention may be melted by the usual methods used in this art, we are able to obtain consistently better control of composition and of ultimate resistance to oxidation by melting the primary melt by either vacuum induction or are melting in air followed by an electroslag remelt step.

In the foregoing general statement of our invention we have attempted to set out certain objects, purposes and advantages of our invention. Other objects, purposes and advantages of this invention will be apparent from a consideration of the following description of certain practices and compositions accordlngto our invention and from the accompanying drawings in which:

F 1G. 1 is a graph of average crack length versus lanthanum content in a 2 92 inch die block;

FIG. 2 is a graph of average crack length versus lanthanum content in a 4 inch die block;

FIG. 3 is a graph of Mils loss versus aluminum content at 2,100F. static oxidation test with various lanthanum contents; and

HO. 4 is a graph of Weight loss versus final aluminum content at 20 00F. Dynamic Oxidation Test.

tion resistance. The test results are set out in Table ll hereinbelow.

ND Not Determined .The oxidation test s of Table ll were identical for all alloys tested. In each case test samples were 0.060 inch ,thick by 2 inches long by three-eighths inch wide.

One group of samples was tested dynamically by exposing the samples at 2,000F. The other group was subject to static oxidation testing at 2100F for four 25 hour periods. The loss was measured and tabulated as above.

Samples A through Hand M through Q were subject to Weldability Tests known in the art as Tig-a-ma-jig". The test procedure is described in Metal Progress, Metal Progress News Supplement, Vol. 100, No. 2, August 1971, p. 7. The results of these tests are compiled in Table III below.

TABLE III TlG-A-MA-JIG WELDABlLlT Y TESTS Average Crack Length (mils) 2% inch Radius Die Block 4 inch Radius Die Block 2.2 2.57 4.03 ND 8.4 ND 1.8 15.7 12.7 21.7 15.3 38.4

ND Not determined The dramatic improvement in results of both oxidation tests and weldability tests is at once apparent from a comparison of alloys A through H (according to the invention) with alloys I through Q (other alloys). This improvement and its unexpectedness is perhaps most clearly apparent from the drawings where FIGS. 1 and 2 show that with lanthanum below about 0.018 percent there is a very short average crack length whereas above 0.018 percent the length increases sharply.

FIGS. 3 and 4 show that maintaining the aluminum content and the lanthanum content in the range here claimed, the oxidation resistance is markedly improved. Thus, the combination of critical lanthanum content and aluminum content produces a surprisingly new alloy modification for welding fabrication of products subject to oxidation.

While we have illustrated and described certain preferred embodiments of our invention in the foregoing specification, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

We claim:

1. A weldable oxidation resistant alloy consisting essentially of by weight about 0.01 to 0.33 percent carbon, up to about 2 percent manganese, up to about 1 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 18 to 30 percent chromium, about 8 to 30 percent nickel, about 8 to 18 percent tungsten, about 0.001 to 0.018 percent lanthanum, about 0.02 to 0.7 percent aluminum, up to about 0.02 percent boron,- up to about 10 percent iron and the balance to 61 percent maximum cobalt with usual impurities in ordinary amounts.

2. An alloy in accordance with claim 1 consisting essentially of by weight about 0.01 to 0.15 percent carbon, up to about 2 percent manganese, up to about 0.6 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 19 to 28 percent chromium, about 10 to 25 percent nickel, about 12 to 18 percent tungsten, about 0.001 to 0.018 percent lanthanum, up to about 0.02 percent boron, up to about 5 percent iron, about 0.02 to 0.5 percent aluminum and the balance cobalt with usual impurities in ordinary amounts.

3. An alloy in accordance with claim 1 consisting essentially of by weight about 0.05 to 0.15 percent carbon, up to about 1.25 percent manganese, about 0.2 to 0.5 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 20 to 24 percent chromium, about 20 to 24 percent nickel, about 13 to 16 percent tungsten, about 0.001 to 0.018 percent lanthanum, up to about 0.015 percent boron, up to about 3 percent iron, about 0.02 to 0.5 percent aluminum and the balance cobalt with usual impurities in ordinary amounts.

4. An alloy in accordance with claim 1 consisting essentially of by weight about 0.10 percent carbon, about 0.65 percent manganese, about 0.35 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 22 percent chromium, about 22 percent nickel, about 14.5 percent tungsten, about 0.001 to 0.018 percent lanthanum, up to about 0.015 percent boron, about 0.02 to 0.5 percent aluminum, up to about 3 percent iron and the balance cobalt with usual impurities in ordinary amounts.

5. An alloy article characterized by resistance to weld cracking and oxidation and made up of an alloy consisting essentially of by weight about 0.01 to 0.33 percent carbon, up to about 2 percent manganese, up to about 1 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 18 to 30 percent chromium, about 8 to 30 percent nickel, about 8 to 18 percent tungsten, about 0.001 to 0.018 percent lanthanum, about 0.02 to 0.7 percent aluminum, up to about 0.02 percent boron, up to about 10 percent iron and the balance to 61 percent maximum cobalt with usual impurities in ordinary amounts. 

2. An alloy in accordance with claim 1 consisting essentially of by weight about 0.01 to 0.15 percent carbon, up to about 2 percent manganese, up to about 0.6 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 19 to 28 percent chromium, about 10 to 25 percent nickel, about 12 to 18 percent tungsten, about 0.001 to 0.018 percent lanthanum, up to about 0.02 percent boron, up to about 5 percent iron, about 0.02 to 0.5 percent aluminum and the balance cobalt with usual impurities in ordinary amounts.
 3. An alloy in accordance with claim 1 consisting essentially of by weight about 0.05 to 0.15 percent carbon, up to about 1.25 percent manganese, about 0.2 to 0.5 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 20 to 24 percent chromium, about 20 to 24 percent nickel, about 13 to 16 percent tungsten, about 0.001 to 0.018 percent lanthanum, up to about 0.015 percent boron, up to about 3 percent iron, about 0.02 to 0.5 percent aluminum and the balance cobalt with usual impurities in ordinary amounts.
 4. An alloy in accordance with claim 1 consisting essentially of by weight about 0.10 percent carbon, about 0.65 percent manganese, about 0.35 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 22 percent chromium, about 22 percent nickel, about 14.5 percent tungsten, about 0.001 to 0.018 percent lanthanum, up to about 0.015 percent boron, about 0.02 to 0.5 percent aluminum, up to about 3 percent iron and the balance cobalt with usual impurities in ordinary amounts.
 5. An alloy article characterized by resistance to weld cracking and oxidation and made up of an alloy consisting essentially of by weight about 0.01 to 0.33 percent carbon, up to about 2 percent manganese, up to about 1 percent silicon, about 0.02 percent maximum phosphorus, about 0.015 percent maximum sulfur, about 18 to 30 percent chromium, about 8 to 30 percent nickel, about 8 to 18 percent tungsten, about 0.001 to 0.018 percent lanthanum, about 0.02 to 0.7 percent aluminum, up to about 0.02 percent boron, up to about 10 percent iron and the balance to 61 percent maximum cobalt with usual impurities in ordinary amounts. 